From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
---|---|
To: | Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: SSI tuning points |
Date: | 2011-06-19 04:25:24 |
Message-ID: | BANLkTinF96Yizb59pe45GyrEvUmviPfJjw@mail.gmail.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
On Fri, Jun 17, 2011 at 5:50 PM, Kevin Grittner
<Kevin(dot)Grittner(at)wicourts(dot)gov> wrote:
> The attached patch addresses one of the open non-blockers for beta3.
>
> These are tuning points which emerged in testing. The first is more
> likely to be helpful. The second may be very important in a few
> types of transaction mixes, but I threw in a lot of weasel words and
> qualifiers because someone could easily try this to bring down the
> transaction retry rate, but suffer a net loss in throughput because
> less efficient plans could be chosen. I hope I made that point in a
> reasonable fashion, although I'm certainly open to suggestions for
> better wording.
This is good advice, but I think it could use a bit more wordsmithing.
How about something like this:
When the system is forced to combine multiple page-level predicate
locks into a single relation-level predicate lock because the
predicate lock table is short of memory, an increase in the rate of
serialization failures may occur. You can avoid this by increasing
max_pred_locks_per_transaction.
A sequential scan will always necessitate a table-level predicate
lock. This can result in an increased rate of serialization failures.
It may be helpful to encourage the use of index scans by reducing
random_page_cost or increasing cpu_tuple_cost. Be sure to <etc.>
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
From | Date | Subject | |
---|---|---|---|
Next Message | Kohei KaiGai | 2011-06-19 07:25:40 | Re: patch: Allow \dd to show constraint comments |
Previous Message | Robert Haas | 2011-06-19 03:53:17 | Re: creating CHECK constraints as NOT VALID |